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Date: Tue, 5 May 2009 17:18:17 +0300
From: Riku Voipio <riku.voipio@iki.fi>
Subject: Re: [Qemu-devel] [PATCH] Revived GUEST_BASE support for usermode
	emulation targets [v3]
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To: Paul Brook <paul@codesourcery.com>
Cc: mika.westerberg@iki.fi, qemu-devel@nongnu.org

On Tue, May 05, 2009 at 02:53:31PM +0100, Paul Brook wrote:
> On Tuesday 05 May 2009, Riku Voipio wrote:
> > +++ b/tcg/x86_64/tcg-target.c
> > @@ -616,15 +616,15 @@ static void tcg_out_qemu_ld(TCGContext *s, cons=
t
> > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0/* movzbl */
> > - =C2=A0 =C2=A0 =C2=A0 =C2=A0tcg_out_modrm_offset(s, 0xb6 | P_EXT, da=
ta_reg, r0, 0);
> > + =C2=A0 =C2=A0 =C2=A0 =C2=A0tcg_out_modrm_offset(s, 0xb6 | P_EXT, da=
ta_reg, r0, GUEST_BASE);

> This breaks when GUEST_BASE is large.

usually we don't set it to very large, just high enough to overcome
mmap_min_addr limits.

> 32-bit x86 is probably ok because GUEST_BASE is always a 32-bit value. =
This is=20
> not true for x86-64. Incidentally tcg_out_modrm doesn't seem to check t=
his,=20
> and silently generates broken code.

Should we rather check for a mazimum size on guest_base or revert to the =
lea -based
version?